I have applied the cascading filters in my attached dashboard in the below structure:-

1) TestDate - Added to context

2) Branch - Added to context

3) Model - All values in context

4) GroupSize - All values in context

5) Protocol - All values in context

6) SanId - All values in context

Here, TestDate filter is the parent filter. So, if i select any date in TestDate Filter, Branch Filter is not automatically picking the latest value (like below screenshot, It's just displaying the old value in parenthesis) from the available relevant values but all relevant values are available when i click the branch filter. Same problem facing from remaining filters also.

This happens when the previous selection in the child filter is no longer available as an option because of the change in the parent filter. So, in your example, Model AF9000 was selected in the Model filter but when you change the Test Date filter, there are no entries for AF9000. Unfortunately, at that point Tableau doesn't know what to do. So it puts the parenthesis around the value in the sub-filter to indicate that the selected value is no longer valid. Personally, I would like to see Tableau reset the sub-filter to "all" in that case...but it doesn't. :-) I don't know of any workaround for this situation.

What Stuart said above is correct. This happens when the previous selection in the child filter is no longer available as an option because of the change in the parent filter.

Best way to handle this would be always save your dashboard with "All" selected for chid filters. This way if you change parent filter, you will not get any value in brackets and list of values in dropdown will be updated to reflect all values based on parent selection.